Soot sensor functional capability monitoring

Abstract

A method of monitoring functional capability of a soot sensor that is responsive to deposition of soot from an exhaust gas stream on a sensor surface comprises acquiring a measurement signal of the soot sensor and running a plausibility check, in which it is ascertained whether the measurement signal agrees with an expected finding. According to the invention it is detected whether conditions are present, on which liquid, e.g. water, from the exhaust gas stream condensates on the sensor surface. Additionally or alternatively, such conditions are produced. The plausibility check then includes ascertaining whether the measurement signal reflects the condensation of liquid. The detection of presence of conditions for condensation comprises a measurement or an estimation of temperature on the sensor surface.

1 . A method of monitoring functional capability of a soot sensor responsive to deposition of soot from an exhaust gas stream on a sensor surface, said method comprising:
 detecting the presence of conditions for condensation of a liquid from said exhaust gas stream on said sensor surface, and if said conditions are present;   acquiring a measurement signal of said soot sensor;   running a plausibility check wherein it is ascertained whether said measurement signal agrees with an expected finding;   wherein said detection of presence of conditions for condensation comprises measuring or estimating the temperature on said sensor surface, and wherein said method does not include the additional step of subjecting the sensor to conditions sufficient to evaporate any condensate and performing any subsequent diagnosis.   
     
     
         2 . The method as claimed in  claim 1 , wherein said detection of presence of conditions for condensation comprises an estimation of temperature on said sensor surface based on
 a) a temperature measurement at another location of the exhaust system and a mathematical model describing thermal properties of the exhaust system or   b) engine parameters used as input parameters of a mathematical model providing the evolution of the temperature of the soot sensor surface as a function of the engine parameters.   
     
     
         3 . (canceled) 
     
     
         4 . The method as claimed in  claim 1 , wherein said plausibility check is run each time the presence of conditions for condensation of said liquid is detected. 
     
     
         5 . The method as claimed in  claim 1 , comprising outputting a warning signal if said plausibility check fails in a predetermined number of successive runs. 
     
     
         6 . The method as claimed in  claim 1 , wherein said soot sensor is arranged in the exhaust gas line of a compression-ignition engine. 
     
     
         7 . The method as claimed in  claim 1 , wherein said plausibility check is run immediately after a cold start of said compression-ignition engine. 
     
     
         8 . (canceled) 
     
     
         9 . A memory device storing instructions which, when executed by a processor, cause said processor to carry out the method as claimed in  claim 1 . 
     
     
         10 . An exhaust gas treatment device for a compression-ignition engine, comprising
 a soot sensor having a sensor surface  4 , said soot sensor being responsive to deposition of soot from an exhaust gas stream on said sensor surface;   a sensor controller operatively connected with said soot sensor to receive a measurement signal from said soot sensor and configured to detect the presence of conditions for condensation of a liquid from said exhaust gas stream on said sensor surface;   said sensor controller being further configured to consequently run a plausibility check that includes ascertaining whether said measurement signal agrees with an expected finding;   wherein said sensor controller is configured to detect   said conditions by measuring or estimating the temperature on said sensor surface, and further configured not to perform any additional step of subjecting the sensor to conditions sufficient to evaporate any condensate and performing any subsequent diagnosis.   
     
     
         11 . (canceled) 
     
     
         12 . The exhaust gas treatment device according to  claim 10 , comprising a particulate filter arranged upstream of said soot sensor. 
     
     
         13 . (canceled) 
     
     
         14 . The exhaust gas treatment device according to  claim 10 , comprising a temperature sensor operatively connected to said sensor controller, said sensor controller being configured to estimate a temperature on said sensor surface based upon a temperature signal received from said temperature sensor. 
     
     
         15 . The exhaust gas treatment device according to  claim 10 , wherein said sensor controller is operatively connected with an engine control unit to receive temperature data or operational data of said compression-ignition engine.